1. Field of the Invention
The present invention relates to a compressor, and more particularly to a compressor arranged in a refrigerating circuit for an air conditioning system of a vehicle.
2. Description of the Related Art
This kind of compressor is used for compressing a refrigerant serving as a working fluid. In general, the refrigerant contains a mist-like lubricating oil, and the lubricating oil serves for not only lubricating sliding surfaces in the compressor, bearings and the like, but also sealing sliding surfaces in the compressor. However, in the case that the lubricating oil contained in the refrigerant is more, the lubricating oil causes to lower refrigerating performance of the refrigerating circuit.
A compressor disclosed in Japanese Unexamined Patent Publication No. 11-82352, therefore, includes a discharge chamber to which a compressed high-pressure refrigerant is discharged, an outlet port for discharging the refrigerant to a circulating path outside the compressor from the discharge chamber, and a separating device for separating the mist-like lubricating oil from the refrigerant, and the separating device is arranged in a delivery path extending to the outlet port from the discharge chamber. In more detail, the separating device includes a separating chamber forming a part of the delivery path, and the separating chamber receives the high-pressure refrigerant from the discharge chamber. The lubricating oil in the refrigerant is partly separated from the refrigerant in the separating chamber on the basis of centrifugal separating effect. The separated lubricating oil is stored in an oil storage chamber, and the oil storage chamber is arranged in a lower side of the separating chamber.
On the other hand, the compressor further includes an intake chamber for supplying the refrigerant to a compression chamber thereof, and the lubricating oil in the oil storage chamber is returned into the intake chamber, and is mixed into the refrigerant in the intake chamber as oil mist.
When the compressor has the separating device therein, an amount of the lubricating oil in the refrigerant discharged to the circulating path from the compressor is small, and it is possible to avoid the refrigerating performance of the refrigerating circuit from being lowered.
As mentioned above, since it is necessary that the separating chamber of the separating device and the storage chamber are secured in the compressor together with the discharge chamber, it is unavoidable that a volumetric capacity of the discharge chamber becomes necessarily small in the case that size of the compressor is fixed.
Further, in order to improve the separating performance of the lubricating oil, it is necessary to accelerate flow speed of the refrigerant introduced into the separating chamber from the discharge chamber. Therefore, the cross sectional area of a jet hole which connects the discharge chamber and the separating chamber has a small.
Further, in order to well lubricate the sliding surfaces and the bearings in the compressor, it is preferable to increase an amount of the lubricating oil returned to the intake chamber. To this end, a lot of lubricating oil is stored in the oil storage chamber.
For the reasons mentioned above, in the case that a load of the compressor, that is, a discharge amount of the high-pressure refrigerant into the discharge chamber is increased, pressure in the discharge chamber is exponentially increased, thereby instantaneously exceeding an allowable maximum discharge pressure of the compressor which causes compression of the lubricating oil in the refrigerant.
On the other hand, the compressor is provided with a relief valve in the discharge chamber, and the relief valve can limit discharge pressure in the discharge chamber to the allowable maximum discharge pressure or less.
However, when an impact pressure such as to instantaneously exceed the allowable maximum discharge pressure is frequently generated in the discharge chamber, the relief valve is erroneously operated so as to be opened every time when the impact pressure is generated, so that the refrigerant including a lot of lubricating oil is ejected to an outer side of the compressor, that is, to an outer side of the circulating path from the discharge chamber. Accordingly, since the refrigerant and the lubricating oil in the circulating path are both reduced, the refrigerating performance of the refrigerating circuit is significantly lowered, and the lubrication in the compressor runs short, whereby malfunction of the compressor is caused.
In order to avoid an improper operation of the relief valve, there can be considered that the relief valve is arranged in the oil storage chamber. However, since a lot of lubricating oil is stored in the oil storage chamber and space above a liquid surface level of the lubricating oil is reduced, the impact pressure generated in the discharge pressure is directly propagated in the space, and the relief valve is improperly operated. In this case, since the lubricating oil is ejected to an outer side of the circulating path from the oil lubricating chamber together with the refrigerant, a lot of lubricating oil is lost from the circulating path.